Conservatories, once the glass-walled playgrounds of wealthy plant collectors, now serve a more urgent function. The changing global climate has spotlighted the role these specialized greenhouses play in preserving plant diversity.

Like zoos for endangered animals, climate-controlled conservatories may well be the only places some plants can survive, allowing scientists to educate the public, including gardeners, about the environmental threats to many species.

Glasshouses, as they are also known, are often the first stop on visitors' tours of public botanic gardens. These structures hint at the research going on behind the scenes, such as the development of seed banks and collections of endangered plants. Conservatories also cost a good deal to operate, and so they stand at the forefront of efforts to use fuel more efficiently.

Kayri Havens, director of plant science and conservation at the Chicago Botanic Garden, says that scientists began viewing species conservation as a primary function of conservatories only about 50 years ago, when they recognized that such threats as habitat destruction, pollution, even overcollecting were endangering plants around the world.

Dr. Havens is among the scientists at botanical gardens who call climate change "an imminent threat to biodiversity." A decade ago, she says, botanists didn't see it as an urgent problem. Today, "Most of my colleagues and I think that we need to complete a concerted seed-bank effort within a decade â€“ two, at most â€“ to capture species while there still is genetic diversity," she says.

The urgency arises from the varying rates at which plant species reproduce, which determines how quickly they can adapt. "We're particularly worried about species such as trees, which take a long time to reproduce," Havens says.

Memo to Noah: Two is not enough

"The prevailing wisdom is that it's better to conserve seeds, when possible, than living plants in a glasshouse," says Havens, because living plants can become genetically impoverished due to inbreeding, succumb to disease, or fail to grow in a greenhouse. "In order to build a conservation collection" â€“ as opposed to a display collection â€“ "it's necessary to have big numbers to capture genetic diversity. A couple of oaks from Russia doesn't make for a conservation collection, but 1,500-plus seeds in a bank does."

As the US coordinator for native seed banking, Havens heads a team that will contribute 30 million seeds, including 1,500 kinds of endangered native tall-grass prairie seeds, to the international Millennium Seed Bank Project and to a similar national project, Seeds of Success. She notes that dried, frozen seeds in airtight envelopes can stay viable for 200 years.

Jan Salick, senior curator of ethnoÂ­botany at the Missouri Botanical Garden, studies how Tibetan people use high-alpine plants on the eastern edge of the Himalayas, where temperatures are rising quickly. The region is experiencing the fastest glacial retreats in the world and dramatic increases in rainfall. High-alpine meadows, rich in biodiversity, contain rare plants. Dr. Salick's field research shows that as temperatures climb, so do plants â€“ they migrate uphill. The ones migrating fastest are not those endemic to the region, but widespread species that reproduce quickly, outcompeting slower-maturing alpine plants.

The snow lotus, for example, which Tibetans regard as an important medicinal plant, takes 10 years to reproduce and must be pollinated by high-alpine bumblebees. Salick has watched this plant diminish in both size and numbers. "Not until after the fact do you get to see the effect of changes in plant communities on such things as the bumblebees and other long-coevolved, intricate relationships with animal species," she says.

Making 'greener' greenhouses

As the climate changes, Salick and others foresee changes in the form and content of conservatories. Tomasz Anisko, curator of plants at Longwood Gardens in Kennett Square, Pa., says the institution, which focuses primarily on horticultural display, renovated its east conservatory in 2006, in part to improve energy efficiency. With each renovation of Longwood's 1920s-era buildings, the heating systems have been updated to heat soil at the root zone and concentrate hot air immediately around the plants, instead of heating the whole space.

Energy use has also inÂ­Â­fluenced which speÂ­Â­cies to display. "In the past, we exÂ­Â­hibited mainly exotic tropical plants that required high temperatures, and we've been replacing them with subtropical and MedÂ­iterÂ­ranÂ­ean plants that can grow in more moderate temperatures," Anisko says, and visitors approve. "That's an important point: You can still design attractive displays and achieve energy savings."

Educating visitors is something Anisko and others believe is a significant opportunity for conservatories. "People don't come to see seeds in the freezer, but to see beautiful plants," Havens observes.

Salick recalls the success story of educating people about the destruction of tropical rain forests. "Public awareness of that issue is amazing," she says. "Kindergartners will ask me about it."

Todd Forrest, vice president for horticulture and living collections at the New York Botanical Garden, says they are targeting average gardeners through an educational program called Gardening in a Changing Climate. "It's important to keep people gardening and give them hope," he says. "Gardens and green spaces are part of the solution to climate change. They provide cool spots, and they store carbon. The more of these we have, the better off our environment will be."

How gardeners adjust to a changing climate

â€œClimatologists tell us that climate change is not as simple as just getting warmer weather,â€ says Todd Forrest, vice president for horticulture and living collections at the New York Botanical Garden. â€œThey predict that it will become warmer year-round, significantly so in winter, but there will also be great variety in precipitation, increased drought, and more frequent extreme precipitation events. This means we have to take a broad approach to keeping gardens healthy.â€

While it is relatively easy to avoid pesticides, gardeners may have a harder time figuring out how to reduce gardening practices that contribute to climate change â€“ and perhaps more worrisome, how climate change is affecting their gardens. Mr. Forrest, who has launched an educational program called Gardening in a Changing Climate, offers guidance in the face of climbing temperatures and â€œweather weirdingâ€ â€“ sudden, often violent, shifts in temperature, wind, and precipitation.

Much of what horticulturists at the New York Botanical Garden have learned from these ventures runs true to the good-gardening practices that have been evolving since the first Earth Day in 1970: â€œWe teach people how to use fuels more efficiently, to choose plants adapted to the local climate, that are drought-tolerant, that arenâ€™t prone to insects and diseases,â€ he says. â€œItâ€™s also important to design gardens that take advantage of the natural topography, instead of fighting it.â€ Rain gardens, for instance, can store water collected on site for use in a later drought.

Unpredictable snowfall, combined with sudden drops in temperature, can mean uncovered plants damaged from freezing, sunburn, and windburn more often than in the past. â€œWe may need to bundle up more of our shrubs in burlap,â€ he says, to make up for the lack of insulating blankets of snow.

At the New York Botanical Garden, Forrest says, â€œWe are removing pavement where we can and looking at permeable pavements and the overall impact of what we do. Itâ€™s not just about temperature, but about the whole landscape.â€

Forrestâ€™s most comforting guidance relates to â€œgardening as a spiritual actâ€ during a confusing and distressing age: â€œGardening keeps people in touch with nature. Some say weâ€™ve always been learning to adapt to changing weather, and we can teach others to do the same thing. Good gardening practices are good for the environment. At first blush, everything we do â€“ whether drive or use electric lights â€“ is part of the problem. But gardens are part of the solution. So we should garden wisely by being as efficient as we can, but we should never feel bad about gardening.â€